1. Field of the Invention
The present invention relates to the movement of bulk materials, and more particularly, pertains to moving and stacking material, such as ore, coal, granite, clay, salt, and potash, generally referred to herein as xe2x80x9caggregatexe2x80x9d, by mobile belt conveyor modules.
2. Description of Related Art
The present invention is concerned with depositing aggregate into piles, and more particularly is an improved system and method for depositing aggregate into multi-lift dump sites, such as heap leach stacks, waste dump sites, or material dump sites, for example.
Prior art systems that perform these functions generally employ material conveyors mounted on bridges or trusses called bridge conveyors, bridges, or mobile stacking conveyors. Articulated mobile conveyors having sections are known. Each section is separately movable relative to the ground. Such a system is described in U.S. Pat. No. 5,749,452 granted May 12, 1998 to Brian M. Kenwisher for Mobile Conveyor Including Alignment System. Very long, endless conveyor belt assemblies are also known for transporting loose particulate material over long distances. These conveyors are only moveable in a direction transverse to their length. Such a conveyor assembly is described in U.S. Pat. No. 4,206,840 granted Jun. 10, 1980 to Raymond D. Hanson for a Movable Belt Conveyor Assembly.
One of the problems with the conveyor systems of the prior art is that such systems take time to move any appreciable distance when a new stack is to be started. This is especially true when stacking aggregate which is to be subjected to heap leach processes. These processes are used, for example, to extract copper or gold from the stacked piles of aggregate or leach pads containing the metal or mineral of interest.
In today""s world, mining is a basic industry in a global economy. Thus, regardless of the site of the mining or leaching operation, it must be conducted in a manner that minimizes capital costs, minimizes operating costs, and minimizes the delay time between stacking heaps and recovering the metals or minerals of interest.
Prior art multiple lift stacking systems using bridges, with either advance or retreat stacking require considerable down time, a great deal of additional earth work effort, and a considerable amount of labor to extend and retract the overland conveyor used in the process. The prior art stacking processes delay recovery of the metals or minerals of interest from the aggregate. In an ongoing leaching operation, for example, a major concern is to leach the newly stacked aggregate immediately. Thus, at the completion of any lift, a complete leach cycle time is scheduled before stacking the next lift so that the material can be leached to full economic advantage at each lift. These concerns, in general, require movement of the prior art systems that could be both wasteful and unnecessary.
A prior art attempt to solve such problem is described in U.S. Pat. No. 6,085,890 granted Jul. 11, 2000 to Ronald R. Kelly, et al. for Heap Leach Stacking Process. However, even this approach requires down time, a shortcoming which the present invention overcomes.
Multiple lift pad and dump site stacking is enhanced in flexibility and speed by the use of mobile stackers, mobile trippers, and mobile conveyor modules, which are carried by rolling stock, such as wheels or crawler tracks which are steerable. Some of these modules are also self-powered so they are driveable to the required locations. The combination of mobile conveyor modules bringing aggregate to a tripper for distribution to a bridge stacker and a radial stacker provides efficient multiple lift stacking of a leach pad or a general dump site. Berm building and corridor filling occur at about the same time as the lift stacking. Moreover, the self-powered mobility of the mobile conveyor modules and tripper modules considerably reduces down time when the modules must be relocated.
The invention utilizes a mobile belt conveyor module mounted for movement with respect to the ground on steerable rolling stock. A mobile belt conveyor with a tripper, xe2x80x9cmobile tripper modulexe2x80x9d mounted for movement with respect to the ground on steerable rolling stock is fed aggregate by the mobile belt conveyor module. A mobile stacker is fed aggregate by the mobile tripper module to stack the aggregate to lift level. The stacking method of the present invention comprises advance stacking a lift berm for conveyor travel at about the same time the extension half of the lift is being advance stacked. The retraction half of the lift is also advance stacked, leaving a completely stacked lift without corridors to be filled. Alternatively, the stacking method of the present invention comprises advance and retreat stacking in the extension phase, creating a corridor for conveyor travel. Advance and retreat stacking in the retraction phase while also stacking the corridor, leaves a completely stacked lift without a corridor to fill.